Immunity is a set of cellular and humoral means of protecting the body from infectious and tumor diseases. It is realized due to the existence of cells such as lymphocytes, plasma cells and macrophages. What it is, you should understand in more detail. The value of these cells is really great for the body and ensuring its vital activity in an aggressive environment.
Origin of macrophages
Macrophage is a cell of bone marrow origin, which, after migration from the vascular bed under the action of cytokines, differentiates into a phagocyte. Strictly speaking, macrophages are phagocytes, that is, cells of active immunity capable of capturing antigens and presenting them on their membranes for plasma cells. They are also able to phagocytize antigens, eliminating them from the body. The monocyte, a cell of bone marrow origin, circulating in the blood, acts as the precursor of this phagocyte. ATmacrophage, it turns after it enters the intercellular space from the vascular bed. Here, under the action of cytokines, its typing occurs.
Macrophage varieties
Macrophages are a type of white blood cell that cannot be found in blood vessels. They are localized in the interalveolar spaces, in the spleen, among the nerve fibers, in the lymph nodes and in the serous membranes. They are also present in large numbers in the intercellular space of other tissues, where they protect them from antigens. Depending on the localization, some types of macrophages are isolated. Varieties of these cells allow you to track which antigens they will be phagocytosed.
The first type of macrophage is the histiocyte. This is the most common type of phagocyte found in many tissues. It is a large cell up to 80 microns in size that captures bacteria, viruses or foreign bodies and digests them.
The second type is lymph node macrophages. In structure, they differ little from histiocytes and perform similar functions.
Resident macrophages
The third type is resident macrophages. A special type of phagocytes that acquire specific features depending on their location. Among the residents, alveolar, Kupffer cells, macrophages of the spleen, and dendritic cells are distinguished. Alveolar macrophages are located in the interalveolar spaces, where they capture bacteria and viruses, eliminating them from the internal environment of the body at its border with the air. Wednesday.
In the case of capturing a solid particle that enzyme systems cannot break down, the macrophage gradually dies. After that, the foreign body is again in contact with the external environment. New macrophages, like immune cells, also try to phagocytize it or form foci of fibrosis around it. This leads to chronic lung disease, especially in smokers and mining workers.
Kupffer and splenic macrophages
Kupffer cells are a specific type of resident macrophages located in the liver. Their task is to destroy blood cells that have been present in the bloodstream for a long time and have lost their significance. The macrophage identifies them by the absence of certain membrane antigens that are lost during the life of the cell. Most often, the Kupffer type destroys many leukocytes, tumor blood cells, erythrocytes.
Splenic macrophages, like Kupffer's, also eliminate erythrocytes and leukocytes from the bloodstream. However, they are located in the spleen. Macrophages of this organ also capture iron and, having accumulated a sufficient amount of it, migrate to the bone marrow, becoming a feeding cell for growing new red blood cells. This demonstrates an example of the transport function that macrophages perform. What is it in terms of histology? Nothing but a feature of tissue differentiation under the action of cytokines.
Dendrite resident macrophages
Macrophage cells located on the border of the epithelium are calleddendritic. Their name comes from the presence of many processes, with the help of which the cell captures a foreign body and is attached between the cytolemmas of other epithelial cells. Dendritic macrophages are located on the border between the vessels and the external environment. In the skin, they are located proximal to the dermis, and in the intestinal and bronchial epithelium, eccentric from the basement membrane.
Features of the structure of macrophages
Considering macrophages (what they are, described above), it is necessary to highlight the key features of their structure. First, they are highly dependent on location. Secondly, they are large. Thirdly, they are mobile and able to migrate to areas of inflammation where there is an increased concentration of cytokines. These structural features should be considered in more detail.
So, macrophages differentiate in place depending on the presence of specific cytokines, and therefore, after their transformation, they receive new receptors and functions. That is, their structure varies depending on the localization. They also come from monocytes, the largest of the blood cells. Therefore, their sizes from 15 to 80 microns are incorporated in them even before differentiation into resident macrophages (what it is is described above). After that, new resident macrophage cells can independently divide in place, already having their own set of affinity molecules to activate phagocytosis without the participation of cellular immunity.
The third feature of the structure is the ability to independently move towards cytokines. Formovement, they have pseudopods, which are also necessary to simplify the formation of a cavity during phagocytosis of a foreign body. They are also able to change their shape, pushing through the capillary fenestra. All this makes the macrophage a universal phagocyte responsible for the direct elimination of foreign bodies in the internal environment of the body.
